1. Field of the Invention
The present invention relates to an improved signal isolator for transmitting a small DC voltage signal in an isolated state, and more particularly to an improved signal isolator having means for isolating a DC voltage signal which has a magnitude of the order of millivolts, as, for example, the electromotive force (emf) of a thermocouple.
2. Description of the Prior Art
Signal isolators known to the art include flying capacitor systems using relay contacts, and transformer isolation systems based on pulse modulation. However, the use of relays creates problems with sampling speed and the length of useful service life because of the mechanical contacts. The pulse modulation isolators are also disadvantageous because they require a plurality of transformers for isolation of both an input signal and a control signal, thus rendering the structure complex.